Study On Numerical Simulation And Risk Assessment Of Multiple Periods Rockfall Movement In Collapse Zone Of River Valley

Guizhou is a mountainous province.Due to the characteristics of karst landforms,frequent geological hazards,such as landsildes avalanche and so on.which is one of the most serious geological disasters in China.The research area of Xujiadabang in Sinan County,there are many avalanche happend in the long geological history.At present,still exist large-scale dangerous rock mass,which is a serious threat to the life and property safety of Xujiadabang residents.Therefore,it is urgent and necessary to carry out corresponding multiple periods avalanche research and risk assessment of research area.In our study,by physical experiments,the physical parameters of slope are found,and will be used for subsequent modeling.Based on the UAV Lidar technology,remove the vegetationg to obtained the high-precision DEM.3D multiple periods avalanche model is constructed by 3D real-scene modeling technology,and a set of research method suitable for multiple periods avalanche is established with Arc GIS software.According to the simulation results of the rockfall movement process in the research area,the risk aof the study area are evaluated,and a set of methods suitable for the risk assessment of the research area in a small area is constructed.The main research results include the following aspects:(1)According to the stratigraphic lithology and topographic slope of the study area,a simple experimental model is built,and the bouncing and friction experiments of irregular falling rocks on different slopes are carried out.The tangential and normal recovery coefficients,collision springback vertical deviation angle,friction coefficient and other physical parameters of different materials are obtained.The purpose of this paper is to provide a reference basis for the slope material assignment of the multiple periods collapse model and the collapse zone model.(2)Making use of the advantage of the combination of Arc GIS software and Roc Pro3 D software,according to the numerical simulation results of each period of collapse,based on the fact that high-precision DEM changes the morphological characteristics of collapse dangerous rock mass and accumulation body in Arc GIS,high-precision modeling data are extracted and three-dimensional simulation model is constructed through Arc GIS,Rhino6,Roc Pro3 D and other software to simulate the movement process of multiple periods collapse and rockfall.After analysis,the simulation results of multiple periods collapse have achieved satisfactory results,and the study of the movement process of multiple periods collapse and rockfall has been preliminarily realized.The research results of this paper can provide reference for the study of this kind of collapse disaster.(3)To establish a set of risk assessment method of rockfall in small area collapse zone.Based on the numerical simulation results of collapse and rockfall,the energy,frequency,acceleration and motion height of rockfall are selected as risk assessment factors,and the weight of evaluation factors is calculated quantitatively by entropy weight method.The hazard distribution map of collapse zone is obtained by using spatial grid superposition technique in Arc GIS,and the envelope is drawn and graded.Finally,the risk area of the study area is divided into four areas: extremely high risk area,high risk area,medium risk area and low risk area.(4)The dangerous situation in the study area is determined on the basis of the number of people and property threatened.According to the results of the division of the risk scope of the study area,the number of threatened people and property in different danger areas are counted respectively,and the danger situation of the study area is divided by referring to the national standard for dividing the risk situation of geological disasters.finally,the study area is divided into two grades: medium-sized geological disasters and small-scale geological disasters.(5)The risk of collapse zone is determined by danger and risk situation.By calculating the risk and risk situation in Arc GIS,the risk area of Xujiadabang collapse zone is obtained,and the risk grade is divided according to the risk assessment matrix.finally,the collapse zone is divided into two areas: medium risk area and low risk area.According to the results of risk assessment,targeted risk prevention and control measures are put forward for the study area.